A0A3B6NKR6

UniProt ID: A0A3B6NKR6
Organism: Triticum aestivum
Review Status: COMPLETE
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Gene Description

A0A3B6NKR6 is a GHMP kinase family protein from Triticum aestivum (bread wheat) that is predicted to function as a glucuronokinase (EC 2.7.1.43) based on its domain architecture. The protein contains GHMP kinase N-terminal (IPR006204) and C-terminal (IPR013750) domains together with a glucuronokinase-like domain (IPR053034). Glucuronokinases catalyze the ATP-dependent phosphorylation of D-glucuronic acid to D-glucuronate-1-phosphate, a key step in the myo-inositol oxidation pathway that provides an alternative route for UDP-glucuronic acid biosynthesis. UDP-glucuronic acid is a critical precursor for UDP-xylose, UDP-arabinose, and UDP-galacturonic acid, which are building blocks for hemicellulose and pectin biosynthesis. In wheat and other grasses with type II cell walls, arabinoxylan is the predominant hemicellulose, making enzymes in the UDP-glucuronic acid supply pathway particularly important for cell wall assembly. The protein is predicted to localize to the cytosol based on pathway context. This protein is unreviewed (TrEMBL) and has not been experimentally characterized; functional assignment rests on domain analysis, homology to characterized GHMP kinases (including Arabidopsis GLAK2, Q9LY82), and metabolic pathway inference.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0005829 cytosol
IBA
GO_REF:0000033 		ACCEPT
Summary: Cytosolic localization is consistent with the predicted glucuronokinase function. The myo-inositol oxidation pathway and UDP-sugar interconversion reactions that glucuronokinase participates in operate in the cytosol, where nucleotide sugar precursors are generated before transport to the Golgi for cell wall polysaccharide assembly. The IBA annotation is phylogenetically inferred from characterized orthologs (with/from includes MGI:MGI:107624 and PANTHER:PTN000048555).
GO:0005524 ATP binding
IEA
GO_REF:0000002 		KEEP AS NON CORE
Summary: ATP binding is well supported for a GHMP kinase family protein. GHMP kinases catalyze ATP-dependent phosphorylation of small-molecule substrates and contain conserved motifs for ATP binding. The InterPro-based IEA annotation from the GHMP kinase N-terminal domain (IPR006204) is appropriate but generic. This represents a necessary cofactor interaction for the predicted glucuronokinase activity rather than the primary molecular function.
Reason: ATP binding is a cofactor interaction intrinsic to kinase activity rather than the defining molecular function of this protein. The more informative annotation would be glucuronokinase activity (GO:0047940), which subsumes the ATP-binding aspect. Keeping as non-core since it is technically correct but not the primary functional descriptor.
GO:0019287 isopentenyl diphosphate biosynthetic process, mevalonate pathway
IEA
GO_REF:0000041 		MARK AS OVER ANNOTATED
Summary: This annotation is based on UniPathway mapping (UPA00057/UER00098) which associates the GHMP kinase domain family with the mevalonate pathway. However, the mevalonate pathway assignment is almost certainly incorrect for this protein. The GHMP kinase superfamily includes both mevalonate kinase and glucuronokinase, but this protein specifically contains a glucuronokinase-like domain (IPR053034), not a mevalonate kinase domain. Additionally, phmmer analysis identifies the closest characterized ortholog as Arabidopsis GLAK2 (Q9LY82, probable glucuronokinase 2, EC 2.7.1.43). The UniPathway mapping appears to be an over-broad family-level inference that incorrectly assigned a mevalonate pathway role based on GHMP kinase membership without considering the specific domain architecture.
Reason: The mevalonate pathway annotation is a family-level electronic annotation that does not account for the protein's specific glucuronokinase-like domain (IPR053034). The protein is most likely involved in UDP-glucuronic acid biosynthesis via the myo-inositol oxidation pathway, not the mevalonate pathway. This is a classic case of over-broad IEA annotation from superfamily membership.
GO:0047940 glucuronokinase activity
IEA NEW
Summary: Not currently in GOA but strongly supported by domain architecture. The protein contains a glucuronokinase-like domain (IPR053034) and its closest characterized ortholog is Arabidopsis GLAK2 (Q9LY82, EC 2.7.1.43). Glucuronokinase activity is the most specific and informative molecular function term for this protein.
Reason: Proposed based on glucuronokinase-like domain (IPR053034) and orthology to Arabidopsis GLAK2. More informative than the current generic ATP binding annotation.
GO:0006065 UDP-glucuronate biosynthetic process
IEA NEW
Summary: Not currently in GOA. Glucuronokinase generates D-glucuronate-1-phosphate, the immediate precursor for UDP-glucuronic acid biosynthesis via the myo-inositol oxidation pathway. This is a more accurate biological process annotation than the current mevalonate pathway assignment.
Reason: Proposed as a replacement for the incorrect mevalonate pathway annotation. UDP-glucuronate biosynthesis is the correct pathway context based on the glucuronokinase-like domain and orthology evidence.

Core Functions

Predicted glucuronokinase that catalyzes the ATP-dependent phosphorylation of D-glucuronic acid to D-glucuronate-1-phosphate in the myo-inositol oxidation pathway, providing an alternative route for UDP-glucuronic acid biosynthesis and supplying nucleotide sugar precursors for cell wall polysaccharide assembly in wheat

Molecular Function:
glucuronokinase activity
Directly Involved In:
UDP-glucuronate biosynthetic process
Cellular Locations:
cytosol
Supporting Evidence:
  • file:WHEAT/A0A3B6NKR6/A0A3B6NKR6-deep-research-falcon.md
    The presence of the glucuronokinase-like domain strongly suggests that A0A3B6NKR6 functions as a glucuronokinase (also known as GluK or glucuronate kinase). Glucuronokinase catalyzes the ATP-dependent phosphorylation of D-glucuronic acid to produce glucuronate-1-phosphate, a key intermediate in the myo-inositol oxidation pathway

References

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External Prediction Reviews

These computational predictions are reviewed separately from the GOA annotation set used for this review. The assessments below are from this project and do not constitute official GO annotations or endorsement by GO/UniProt. They are not included in the existing annotation review above.

ProtNLM2 External predictions

View prediction review YAML · A0A3B6NKR6-protnlm-predictions-review.yaml · Review status: COMPLETE

The GHMP kinase architecture and glucuronokinase-like family assignment support broad phosphorylation without establishing a specific substrate.

Source documents: genes/WHEAT/A0A3B6NKR6/A0A3B6NKR6-uniprot.txt · genes/WHEAT/A0A3B6NKR6/A0A3B6NKR6-goa.tsv · publications/PMID_19951951.md

Review score: 2 = concordant with evidence; 1 = uncertain; 0 = discordant with evidence. This is an assessment score, not a model probability.

GO:0016310 phosphorylation GO_BP
COR — Correct novel prediction Review score: 2/2
Prediction method: ProtNLM2 · Version: UniProt 2024_06 pilot
Review rationale: The target contains both GHMP kinase domains and a glucuronokinase-like family assignment. Purified and recombinant plant glucuronokinase catalyzes ATP-dependent sugar phosphorylation (PMID:19951951), providing functional grounding for broad phosphorylation in this family. This does not establish the target's precise substrate or the mevalonate-pathway assertion in the electronic annotations. The predicted process is absent from the cached annotations, and there is no supported more specific phosphorylation process that makes it less precise.
Supporting Evidence:
  • file:WHEAT/A0A3B6NKR6/A0A3B6NKR6-uniprot.txt: "ID A0A3B6NKR6_WHEAT Unreviewed; 360 AA. ... DR GO; GO:0005829; C:cytosol; IBA:GO_Central. ... DR InterPro; IPR013750; GHMP_kinase_C_dom. ... DR InterPro; IPR006204; GHMP_kinase_N_dom. ... DR InterPro; IPR053034; Glucuronokinase-like. ... FT DOMAIN 97..181 ... FT /note="GHMP kinase N-terminal" ... FT DOMAIN 257..327 ... FT /note="GHMP kinase C-terminal""
  • PMID:19951951: "It requires ATP as phosphate donor"

Deep Research

Falcon

(A0A3B6NKR6-deep-research-falcon.md)

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